scholarly journals Investigation of Operational Efficiency using Stochastic Models for Electric propulsion in Ships

2020 ◽  
Vol 2 (2) ◽  
pp. 84-91
Author(s):  
Nayana
Keyword(s):  
Stochastic Models ◽  
Electric Propulsion ◽  
Operational Efficiency ◽  
Installation Space ◽  
Energy Output ◽  
Drive Trains ◽  
Recent Developments ◽  
Consumption Energy ◽  
Traction Equipment ◽  
Operational Processes

In various models of vehicle drive trains, issues such as improving electric propulsion reliability, environmental performance, and economic efficiency has been enabled by the recent developments in electric power engineering in terms of materials, equipment and technologies. The increasing requirements in ecological parameters, efficiency for fault tolerance and reliability, accurate selection of design features and type of electric propulsion drive as well as the limitations on the traction equipment weight and installation space are the important parameters for execution of the system approach. The automobile electric propulsion systems consisting of one or more traction motors and few generating elements and their operational efficiency are analysed by means of stochastic models. Aircrafts, hybrid cars, diesel-electric locomotives, arctic cargo ships and icebreakers are ideal platforms for implementation of the propulsion system. The load modes of traction electric motors, operational fuel consumption, energy output of thermal engines and several other probabilistic characters of operational processes and random factors that influence the simulation result accuracy cannot be evaluated using the deterministic approach.

Approximating a Cumulative Distribution Function by Generalized Hyperexponential Distributions

1997 ◽  
Vol 11 (1) ◽  
pp. 11-18 ◽  
Author(s):  
Jihong Ou ◽  
Jingwen Li ◽  
Süleyman Özekici
Keyword(s):  
Distribution Function ◽  
Performance Measures ◽  
Stochastic Models ◽  
Queueing Theory ◽  
Cumulative Distribution Function ◽  
Cumulative Distribution ◽  
Idle Period ◽  
Period Distribution ◽  
Different Types ◽  
Recent Developments

Recent developments in stochastic modeling show that enormous analytical advantages can be gained if a general cumulative distribution function (c.d.f.) can be approximated by generalized hyperexponential distributions. In this paper, we introduce a procedure to explicitly construct such approximations of an arbitrary c.d.f. Although our approach can be used in different types of stochastic models, the main motivation comes from queueing theory in obtaining approximations of the idle-period distribution and other performance measures in GI/G/1 queues.

scholarly journals Design of a Superconducting Machine and its Cooling System for an Aeronautics Application

2020 ◽  
Author(s):  
Alexandre Colle ◽  
Thierry Lubin ◽  
Jean Leveque
Keyword(s):  
Electric Propulsion ◽  
Cooling System ◽  
High Temperature Superconductors ◽  
Cryogenic Cooling ◽  
Electrical Machines ◽  
High Magnetic Fields ◽  
High Power Density ◽  
Optimal Temperature ◽  
Recent Developments ◽  
Electrical Motors

The transition to electric propulsion aircraft requires electrical motors or generators with high power density. The “zero resistivity” of the superconducting materials could be used in electrical machines to produce high magnetic fields and reduce the use of heavy components such as the ferromagnetic parts. The discovery and recent developments in High Temperature Superconductors (HTS) technology make the superconducting machine a serious candidate in the future of aircraft. The design of a superconducting machine is strongly dependent on its electromagnetic and thermal behavior. In this paper, the design of a 50 kW superconducting aircraft generator is presented. The mass of the cryogenic cooling system is included into the design in order to optimize the entire superconducting system. The study shows that the optimal temperature which conduct to the lighter superconducting system depends on the power of the superconducting machine.

Energy transfer through parametric excitation to reduce self-excited drill string vibrations

2021 ◽  
pp. 107754632110310
Author(s):  
Vincent Kulke ◽  
Georg-Peter Ostermeyer
Keyword(s):  
Energy Transfer ◽  
Parametric Excitation ◽  
High Frequency ◽  
Drill String ◽  
Alternative Methods ◽  
Installation Space ◽  
Energy Output ◽  
Torsional Oscillations ◽  
Bottom Hole ◽  
Bottom Hole Assembly

Drilling a wellbore can result in several types of vibration that lead to inefficient drilling and premature failure of drill string components. These vibrations are subdivided based on their operating direction into lateral, torsional, and axial vibrations. Especially in hard and dense formations, high-frequency torsional oscillations are found in the bottom-hole assembly (BHA). These critical vibrations are induced by a self-excitation mechanism caused by the bit–rock interaction. Self-excitation mechanisms are regenerative effects, mode coupling, or a velocity-dependent torque characteristic at the drill bit. To increase drilling performance and reduce tool failure due to high-frequency torsional oscillations, the critical vibration amplitudes localized at the bottom-hole assembly need to be minimized. Increasing the damping of self-excited systems to affect the energy output during vibration is a common approach to mitigate self-excited vibrations. In drilling systems, the achievable damping is naturally limited by the small installation space due to the drilled borehole diameter. Therefore, alternative methods to influence vibrations are necessary. Applying parametric excitation in self-excited systems can result in a parametric anti-resonance and therefore in an energy transfer within different modes of the structure. This allows, among other benefits, improved utilization of the structural damping. In this article, the influence of additional stiffness–based parametric excitation on self-excited torsional vibration in downhole drilling systems is investigated. For this purpose, a finite element model of a drill string is reduced using the component mode synthesis and analyzed with the goal to mitigate torsional vibrations. The multiple degree of freedom drill string model is investigated regarding the additional energy transfer due to the parametric excitation. Robustness of various parameters, especially with regard to the positioning within the bottom-hole assembly, is analyzed and discussed. Additionally, the problem of multiple unstable self-excited modes due to the nonlinear velocity-dependent torque characteristic in drilling systems is addressed.

scholarly journals Recent Developments on Ethylene Dimerization with Focus on Alphabutol Optimization

2019 ◽  
Vol 8 (10) ◽  
pp. 3969-3975
Keyword(s):  
Heat Exchanger ◽  
Ethylene Dimerization ◽  
Research Technology ◽  
Area Of Interest ◽  
Significant Area ◽  
Recent Developments ◽  
Time Required ◽  
Operational Issues ◽  
Operational Processes ◽  
And Control

Butene-1 is an essential compound or co-monomer typically used to regulate and control the density of both high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE). The production of Butene-1 has become a significant area of interest to the industrial and educational-research sectors. Alphabutol technology is one of the Butene-1 production processes. This paper attempts to find a problem that has not been addressed by previous research on production of Butene-1 by using ethylene demineralization route focussing on Alphabutol Technology. The first part of this paper is on the ethylene dimerization techniques available in the literature. Most research on the ethylene dimerization technique emphasized on how to enhance the selectivity of Butene-1 from ethylene using different types of catalyst. The second part of this paper reviews the operational processes used to minimise fouling reported in the literature review. Most of the literatures focused ethylene dimerization and not on the operational issues to be overcome during chemical reactions to enhance the selectivity of Butene-1. Fouling problem in Alphabutol process is still an area that is not adequately addressed in the literature. There is also no literature on operating or maintenance procedure to address these problems of the technology. Therefore, there is still room for improvement on the ethylene dimerization research technology, particularly in the operational process and conditions where the improvement in the reaction parameters of the Alphabutol reactor can improve selectivity of butene-1, extend the run time of the heat exchanger and reduce the time required to clean the heat exchanger fouling.

Technological Advances to Maximize Solar Collector Energy Output: A Review

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Swapnil S. Salvi ◽  
Vishal Bhalla ◽  
Robert A. Taylor ◽  
Vikrant Khullar ◽  
Todd P. Otanicar ◽  
...  
Keyword(s):  
Solar Energy ◽  
Fossil Fuels ◽  
Semiconductor Industry ◽  
Solar Thermal ◽  
Energy Output ◽  
Solar Collectors ◽  
Selective Coating ◽  
Technological Advances ◽  
Recent Developments ◽  
Highly Correlated

Since it is highly correlated with quality of life, the demand for energy continues to increase as the global population grows and modernizes. Although there has been significant impetus to move away from reliance on fossil fuels for decades (e.g., localized pollution and climate change), solar energy has only recently taken on a non-negligible role in the global production of energy. The photovoltaics (PV) industry has many of the same electronics packaging challenges as the semiconductor industry, because in both cases, high temperatures lead to lowering of the system performance. Also, there are several technologies, which can harvest solar energy solely as heat. Advances in these technologies (e.g., solar selective coatings, design optimizations, and improvement in materials) have also kept the solar thermal market growing in recent years (albeit not nearly as rapidly as PV). This paper presents a review on how heat is managed in solar thermal and PV systems, with a focus on the recent developments for technologies, which can harvest heat to meet global energy demands. It also briefs about possible ways to resolve the challenges or difficulties existing in solar collectors like solar selectivity, thermal stability, etc. As a key enabling technology for reducing radiation heat losses in these devices, the focus of this paper is to discuss the ongoing advances in solar selective coatings and working fluids, which could potentially be used in tandem to filter out or recover the heat that is wasted from PVs. Among the reviewed solar selective coatings, recent advances in selective coating categories like dielectric-metal-dielectric (DMD), multilayered, and cermet-based coatings are considered. In addition, the effects of characteristic changes in glazing, absorber geometry, and solar tracking systems on the performance of solar collectors are also reviewed. A discussion of how these fundamental technological advances could be incorporated with PVs is included as well.

Recent developments in electric propulsion in the USSR

1983 ◽  
Author(s):  
V. ZHURIN ◽  
A. POROTNIKOV ◽  
S. BORISOVA
Keyword(s):  
Electric Propulsion ◽  
Recent Developments
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